1. Technical Field
The present invention relates to the creation of a holographic media display system that combines physical media or digitally stored files with a digital holographic player hardware system. The result is the creation of a compact and portable multimedia holographic viewing experience.
2. Background Art
A hologram is a microscopic pattern of interference fringes, representing an interaction of two beams of coherent light. Therefore, the hologram is a photographic registration of the interference pattern formed by the two beams, with one of the beams consisting of scattered light from a physical object. Once properly illuminated, the hologram may produce a three dimensional image of the physical object. In recent years, a great deal of effort has been put forth towards developing displays using holography techniques.
FIGS. 1A and 1B depict a side and top view, respectively, of an example of a holographic film printing process. A coherent light source 101, or laser, provides a pulsed beam 103. The pulsed beam 103 is then split into two identical beams, an object beam 109 and a reference beam 107, via a beam splitting cube 105. The object beam 109 is then deflected, via a mirror 111, onto a beam expander consisting of a lens 113 and an aperture 115. The resultant diverging beam 117 is then sent through an optical system 119, which is used to maintain a uniform intensity across the planes of coherent light 121, at which the object will be placed. In the present example, the object is a frame from a movie film 123. The film 123 may be held in place by transparent plates 127 and 125. An anti-reflection exit surface 134 may be used to reduce reflections.
Once the object beam 121 has passed through the film 123, a modified object beam 129 will be emitted through the anti-reflection exit surface 134. The modified object beam 129 carries imaging information of the object. The modified object beam 129 is then directed towards a photosensitive hologram detector strip 141. The photosensitive hologram detector 141 is placed behind a mask 143 and is enclosed by transparent members 137 and 139.
The modified object beam 129 is combined, or interfered, with a diverging reference beam 135 at an aperture 145 of the mask 143. The diverging reference beam 135 is obtained by directing the reference beam 107 through a lens 131. The lens 131 brings the beam to a point focus in an aperture 133 resulting in the divergence. The interference of the diverging reference beam 135 and the modified object beam 129, at a finite angle θ, forms a holographic pattern each time the coherent light source 101 is pulsed. Therefore, for every pulse of the laser 101, a single movie frame may be recorded as a single holographic image.
An electronic control 147 may be used to advance the movie film 123 with the use of a motor 149 and rollers 153. The electronic control 147 may also be used to advance the photosensitive hologram detector strip 141 with the use of a motor 151 and rollers 155. Synchronization of the laser pulsing, the advancement of the movie film 123, and the photosensitive hologram detector strip 141 may also be achieved via the electronic control 147.
FIG. 2 provides an illustrative example of a portion of the photosensitive hologram detector 200. The detector comprises a strip 241 (or 141 in FIGS. 1A, 1B) consisting of a number of rows. Each row, for example row 201, comprises a single hologram representing a movie frame. The hologram comprises luminance information as well as color information used in the image reconstruction process.
FIG. 3A depicts a hologram display apparatus 300. A converging coherent beam 301 is passed through an aperture 303 onto the holographic detector strip 341 at a reconstruction angle θ. In holographic reconstructions, the same laser and angle employed for the recording process, is typically used. The illumination of the holographic detector strip 341 results in the reconstruction of two images, a luminance signal image 307 and a color signal image 305. Two raster scan type image detecting tubes 309 and 311 are positioned to receive the signals 305 and 307, respectively. The detecting tubes produce time varying electrical signal outputs based on the signals 305 and 307. Bandpass filters 315, 319, and 323 allow for the transmission of blue, red, and green carrier frequency signals, respectively, to pass. The luminance (Ey), blue (EB), red (ER), and green (EG) electrical signal outputs 313, 317, 321, and 325 are then passed on to signal processing devices and eventually sent to a receiver antenna for a two-dimensional display, similar to that of a standard television.
Other forms of holographic media storage have also been explored, for example, Holographic Versatile Discs (HVD). HVDs are typically used for document storage and allow for the reconstruction of a two-dimensional holographic image. HVD systems are based on an optical disc technology that employs a technique known as collinear holography. In collinear holography two lasers, typically one red and one blue-green, are collimated in a single beam. The blue-green laser reads data encoded as laser interference fringes from a holographic layer near the top of the disc. The red laser has the dual function of being used as a reference beam, as well as to read servo information from a regular CD-style aluminum layer near the bottom. Servo information may be used to monitor the position of the read head over the disc, similar to the head, track, and sector information on a conventional hard disk drive. On a CD or DVD, this servo information is interspersed amongst the data.
FIG. 3B provides an example of how a HVD holographic media file may be recorded. The top layer of the HVD, or the volumetric recording layer 350, is the portion of the HVD where the holographic media files 351 are stored. Each media file 351 represents a page of data 352. As is shown in FIG. 3B, an HVD may store holograms in overlapping patterns, while using the servo information to access a desired page.
In contrast, a DVD will typically store bits of information side-by-side. An HVD makes use of a thicker recording layer than that of a DVD. The HVD also utilizes almost the entire volume of the disk, instead of just a single thin layer. Therefore, HVD systems may store approximately 200 times the amount of information a DVD is capable of storing.